1. Field of the Invention
This invention relates to an engine output control system for a vehicle for controlling the engine output torque characteristics according to the operating condition of the engine.
2. Description of the Prior Art
As disclosed, for instance, in Japanese Unexamined Patent Publication No. 63(1988)-50623, there has been known an engine in which the output torque of the engine is limited in the high engine speed heavy load range and is increased in the middle engine speed range by controlling the relief pressure of a supercharger and controlling the supercharging pressure according to the engine speed in view of durability of the engine.
However in an engine having a particular output torque characteristic curve such as those having a torque peak in the middle engine speed range, when the vehicle is to be accelerated over the torque peak, the torque cannot be smoothly increased and feeling of smooth acceleration cannot be obtained.
That is, when the engine has a torque characteristic curve which is fixed irrespective of manner of acceleration and has a torque peak in the middle engine speed range, fall of the output torque in the high engine speed range adversely affects the acceleration and the feeling of acceleration which the driver experiences is not satisfactory during acceleration from a low speed.
On the other hand, when the torque peak in the middle engine speed range is lowered so that the torque characteristic curve is flat in order to improve the feeling of acceleration during acceleration from a low speed, initial torque becomes too low and the feeling of acceleration deteriorates when the vehicle is accelerated from the middle speed range at a high gear-speed such as top gear.
Further, in the case of an engine which has a torque characteristic curve having a torque peak in each of the low engine speed range and the high engine speed range, the feeling of acceleration which the driver experiences is not satisfactory due to fall of the output torque in the middle engine speed range when the vehicle is accelerated from a low speed.